This invention relates to improvements in transmission means and more particularly to a unique transmission system having means to govern the drive speed of its input shaft in accordance with the speed of its output shaft. The transmission is therefore output speed controlled.
The transmission of the present invention has many applications. By way of example, it may be used as the transmission for self-propelled vehicles such as automobiles, mini-bikes, snowmobiles and pedal operated vehicles. It may also be used in association with the drive means in various types of machinery. In addition, it may serve as a speed governor. For purposes of illustration, the transmission of the present invention will be described in respect to various of its applications and particularly with reference to pedal operated vehicles. However, it will be obvious that the application is not so limited and such is not intended.
In efforts to produce more efficient transmissions, prior art workers have devised a number of means to control drive train ratio. These controllers, however, are responsive to the input shaft speed. Furthermore all prior control systems related to control of drive train ratios known to applicants require an increase in the speed of the input shaft of the transmission to produce an increase in the speed of its output shaft.
For example, in a standard hydraulic automatic transmission in automotive applications, the gear train ratio is controlled primarily by the speed of the automobile engine. That is, by increasing engine speed, hydraulic pressure changes effect change in the transmission ratio and the transmission output speed is correspondingly increased. In conventional pulley belt transmissions, centrifugal weights or the like in the transmission input shall effect a decrease in pulley ratio with an increase in the input shaft speed.
The present invention is directed to an output speed-controlled transmission wherein the control of the respective speeds of the input and output shafts is determined by means in association with the transmission output shaft and responsive to its speed. The invention transmission may be so designed as to effect an increase in the speed of rotation of the input shaft in correspondence with and as a result of the speed of rotation of the output shaft. In addition, however, it offers two distinct capabilities, after initial start-up, not inherent in conventional systems. The output speed controlled transmission may be so designed as to have the input shaft turned at a speed which is decreased in respect to the output shaft speed and vice versa. The transmission may also be arranged to maintain a constant speed at the input shaft with an increasing output shaft speed.
A prime feature of the invention is its inherent capabilities in diminishing air pollution in use of an internal combustion engine.
In the automotive field, for example, much attention has recently been given to the problems of emissions control. One of the primary difficulties lies in the fact that for each automotive engine speed there are many variables (such as air-fuel ratio, spark advance, cam timing and the like) to be considered for the minimizing of emissions. Since the optimum conditions of these variables will change for different engine speeds, it is substantially impossible to design an engine which optimizes the variables to produce minimum emissions for the full range of operating engine speeds. Through the use of the transmission of the present invention, however, the engine speed could remain at a predetermined constant regardless of the vehicle speed (after an initial change of engine speed during startup) and the variables could be adjusted to give minimum emissions at that predetermined speed. Furthermore, this predetermined engine speed could be so chosen as to cause the engine to operate at its maximum power output speed, regardless of the automobile speed.
In a number of vehicles, such as minibikes, snowmobiles and the like, which currently employ pulley belt systems, the engine speed increases with vehicle speed with the result that the vehicle speed is limited by the engine speed and not by the power required to drive the vehicle at high speed. Through the use of the transmission of the present invention, the maximum speed potential of such vehicles could be realized since at high vehicle speeds the engine could be made to operate at a safe speed at which it produces maximum horsepower.
Pedal powered devices such as bicycles and the like are prime examples of vehicles, the speed of which is limited by the input speed. To overcome this problem, prior art workers have devised systems employing up to 15 different gear ratios. These systems are complex, however, and require the slipping of a chain from one gear to another to effect a ratio change. The application of the present transmission to a bicycle would enable the cyclist to pedal at a constant speed (after an initial startup phase) regardless of the bicycle speed and no manual gear changes would be required. This will be particularly described.
The transmission of the present invention may also be used with many types of electric motor-powered devices. When an electric motor is used to drive a piece of equipment characterized by high inertia, the electric motor tends to accelerate to its operational speed before the equipment during startup. This, in turn, can result in excessive belt slippage. Through the use of the present transmission, the motor could operate at its maximum power speed during startup without belt slippage.
The output speed-controlled transmission of the present invention, in preferred embodiment, is of the pulley belt type, but contrary to the usual prior art structures, it does not require skewing of the belt and consequent accelerated belt wear. The transmission may be provided with manually or automatically controlled override means, as will be described hereinafter. Furthermore, it may employ various types of shaft speed sensors, again as will be described hereinafter.